In general, wheel loaders are not provided with a suspension system for absorbing vibration of a vehicle body in order to efficiently utilize driving force for works such as digging. Therefore, chances are that a load such as earth and sand, loaded on a work implement (e.g., a bucket) attached to the tips of a pair of booms, drops due to vibration of the vehicle body during travelling.
In view of the above, methods of providing a travel damper formed by boom cylinders and an accumulator communicated with the boom cylinders have been proposed (see Japan Laid-open Patent Application Publication Nos. H05-209422 and 2007-186942). In the method described in Japan Laid-open Patent Application Publication No. H05-209422, the accumulator is configured to be coupled to the boom cylinders when the vehicle speed of a wheel loader is greater than or equal to a predetermined value. In the method described in Japan Laid-open Patent Application Publication No. 2007-186942, a control of accumulating pressure in the accumulator is executed depending on at least either of the vehicle speed of the wheel loader and a position of a front/rear travel lever.